1. Field of the Invention
The present invention relates to trestles and support structures useful in the construction trades, and particularly to an adjustable saw horse useful in painting, carpentry, residential construction, and the like.
2. Description of the Related Art
The saw horse is a general purpose support device well known in the construction trades. A typical saw horse includes two pairs of legs with a cross beam mounted between the pairs, each pair of legs describing a generally triangular shape with the ground. At least one board may be disposed on top of a pair of saw horses, either as a work piece or as a work surface or as a small scaffolding. The portability, versatility, and economical construction of saw horses provide great utility.
It has long been noted that the convenience and functionality of the saw horse may be improved by departing from rigid structural designs. It has been found desirable to provide the saw horse with pivoting or collapsible members for convenient storage, and with some means for adjusting the height of the saw horse for various applications. It is further desirable to construct a saw horse from light weight materials to provide ease in transportation. Yet another desirable feature is some means for maintaining the saw horse in a stable and balance position on a sloping ground surface. Various modifications in the design and construction of saw horses have been proposed to accomplish these objectives.
U.S. Pat. No. 926,320, issued Jun. 27, 1909 to M. Croner teaches a saw horse with a wooden cross beam and 2 wooden uprights having a metal covering on the sides joined by two right angle brackets, diagonal braces or struts between the cross beam and the uprights, and a metal casing triangular in shape having two legs screwed to the exterior sides of the casing and a socket on the interior of the casing adapted for receiving the upright, the height of the saw horse or trestle being adjusted by sliding the uprights in the socket of the metal casing and securing the upright by a screw pressing against the metal covering of the upright.
U.S. Pat. No. 962,976, issued Jun. 28, 1910 to Pence, et al., discloses another saw horse made primarily from wood, including a cross beam and 2 vertical uprights joined by a U-shaped fitting at either end and having diagonal braces or struts between the cross beam and the uprights, two pairs of pivotally mounted supporting legs at either longitudinal end of the cross beam, cross bracing between one leg of each pair of legs on the same side of the cross beam longitudinally, braces between the legs of each pair of legs, optional leg extensions, metal sockets adapted for receiving the uprights, and a ratchet and pawl assembly connected to the socket for adjusting the height of the saw horse.
U.S. Pat. No. 1,851,668, issued Mar. 29, 1932 to P. E. Goodwin, discloses a trestle made from angle steel, each pair of legs being an integral unit generally V-shaped, two vertical standards, braces between the legs of each pair of legs, a wooden cross beam, diagonal struts between the uprights and the cross beam, and a ratchet and pawl mechanism for adjusting the height of the trestle.
U.S. Pat. No. 4,565,263, issued Jan. 21, 1986 to T. J. Southworth, describes a saw horse made from metal except for a wooden cross beam, having square, tubular, telescoping legs, triangular shaped gussets bracing the legs and cross beam longitudinally and transversely, feet consisting of circular shoes with rubber pads to frictionally engage the surface, the legs having stop plates to stop their travel in either direction and bolts extending through the legs and a hole in the stop plate to lock the telescoping legs in order to adjust the height of the saw horse.
U.S. Pat. No. 4,782,917, issued Nov. 8, 1988 to R. H. Schulz, teaches a saw horse or trestle which may be used individually, rather than in pairs, having a rectangular frame between two pairs of legs and a rectangular platform on top of the frame, with supports arms secured by clamps to adjust the height of the platform, telescoping legs secured by a bolt and wing nut to adjust the height of the legs, and a cross brace between legs on opposite sides of the platform. One edge of the rectangular frame comprises a step, and a brace between the legs comprises a second step, forming a ladder to reach the raised platform. The device can be folded and locked in the folded position.
U.S. Pat. No. 4,804,064, issued Feb. 14, 1989 to Coultrop, et al., teaches a cross beam composed of two telescoping aluminum sections locked by a resilient spring biased button, tubular telescoping legs locked by a U-shaped spring clip, the length of the legs being independently adjustable to compensate for uneven ground surfaces, and end brackets, triangular in shape, disposed between the legs and the cross beam. Each leg is attached to the end bracket by a rivet in order to rotate parallel to the cross beam for storage.
U.S. Pat. No. 4,877,109, issued Oct. 31, 1989 to Welch, et al., shows a saw horse with telescoping legs having feet parallel to the bottom of the cross beam, a brace between legs on opposing sides of the crossbeam, the legs being square and tubular in cross section, the legs being attached to a tubular support through which the cross beam slides, a rack parallel to the cross beam for holding and clamping a work piece, and, optionally, a board may be extended longitudinally supported by the leg braces to form a step.
French Patent No. 758,234, published Jan. 12, 1934, shows a trestle for scaffolding with 2 pairs of legs, each pair being pivotally mounted on a gusset which also supports a vertical tube into which supports for the cross beam telescope. The trestle includes cross bracing between the legs, and the legs fold for storage by pivoting on the gusset.
The present invention presents novel improvements in an adjustable saw horse not disclosed in the prior art. The present invention includes an aluminum channel extending between two pairs of telescoping legs, a wooden cross beam being rigidly secured within the channel. The aluminum channel lends additional support to the cross beam to withstand bending and shear stresses in order to withstand a greater load than beams which are connected in the middle, such as the Coultrop patent.
The present invention also includes a brace between adjacent legs at each end of the saw horse which is adjustable in length. This allows the separation at the base of each pair of legs to be adjusted to correspond to a lengthening or shortening of the telescoping legs, since the length of the brace may be adjusted, presenting an A-frame as viewed from the end. Prior inventions such as the Croner, Pence and Goodwin patents accomplish adjustment in the height of the saw horse by raising or lowering vertical uprights supporting the cross beam. In effect, this creates a beam supported on columns rising above the apex of the triangles formed by the pairs of supporting legs and the ground, thereby subjecting the beam to increased shear and bending stresses, and limiting the maximum height due to the risk that the base of the saw horse may become unstable and topple over. The present invention permits a greater height adjustment by broadening the base of the supporting legs while maintaining an A-frame brace between the legs.
A further feature of the present invention is the provision of pivotally mounted feet at the base of the legs of the saw horse, the feet having serrated edges adapted for penetrating the ground. Previously the only method of adjusting a saw horse to maintain a level work piece on sloping ground has been to extend the length of one or more legs, as in the Coultrop patent. While that may also be done with the present invention, the present invention also provides pivoting feet which are adapted for penetrating the ground in order to firmly anchor the saw horse on sloping ground in order to prevent the saw horse from tipping over and in order to maintain the saw horse in a firm and level position.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the improved features of the instant invention as claimed. Thus a adjustable saw horse solving the aforementioned problems is desired.